The corrosion of steel and other metal containing products continues to be a serious technical problem that has profound effects on the economy. Corrosion causes loss of natural resources, and deteriorates key infrastructure such as roads and buildings. It also causes premature replacement of equipment and parts in industrial facilities, boats and other marine vehicles, automobiles, aircraft, among a wide range of metallic components.
Current industry standards for corrosion prevention center around the use of barrier coatings, sacrificial coatings, alloys containing heavy metals such as chromium, nickel, lead, cadmium, silver, copper, mercury, and barium, among other heavy metals. However the introduction of these materials into the environment can lead to serious health consequences as well as substantial costs to contain or separate the materials or clean up environmental contamination. In addition, the application of these coatings frequently requires the use of organic solvents that can themselves pose environmental concerns.
Various proposals have been made to develop improved surface coating compositions for metallic materials without using organic solvents; for example, the use of coating compositions containing cement mortar. However, the use of cement mortar causes problems in that cracks occur in the protective coatings with the elapse of time and various desired characteristics such as mechanical strength, impact resistance, abrasive resistance, and acid resistance are not obtained. Furthermore, although the addition of various synthetic resin emulsions into the surface coating compositions containing cement mortar has been proposed, the desired characteristics such as water resistance, saline water resistance, weathering resistance, and impact resistance have generally not been obtained. Furthermore, the glossiness and smoothness are unsatisfactory and, therefore, when these surface coating compositions are applied to the surface of metallic materials, the natural metallic luster is impaired.
There is therefore a continuing need for improved protective coatings, and paints for and methods of producing the same, that resist.
In U.S. Pat. No. 4,875,938 there is described a method of making a cementitious binder for use in mortars comprising heating marine shell material to about 2100 to 2350° F. (1150 to 1290° C.); allowing the shell material to cool to ambient temperature; mixing water with the cooled shell material in the ratio of about one part of water by volume to about five parts of shell material by volume; allowing said mixture to spontaneously heat; and monitoring the heat level of said mixture until it commences to cool and as it cools is converted into a dry, substantially white, powdery material that is substantially of the consistency of talcum powder and is useful as a binder in mortar.
Although the mechanism of the processes involved in the production of the cementitious binder described in U.S. Pat. No. 4,875,938 are not fully understood, it is believed that heating of the marine shell to high temperature converts calcium carbonate in the shell to calcium oxide and then the subsequent treatment with water converts the calcium oxide to calcium hydrate, a highly exothermic reaction.
According to the present invention it has now been found that the powdery product of the process described in U.S. Pat. No. 4,875,938 is useful in producing protective coatings on metal surfaces, which coatings are resistant to oxidation of the metal. Moreover, these coatings do not exhibit the tendency to crack experienced with coating compositions containing cement mortar. Moreover, it has been found that the process of U.S. Pat. No. 4,875,938 can be used with a wider variety of animal skeletal materials than shells thereby markedly expanding the scope of raw materials that can be used in the process.